CdO epitaxial layers grown on (0 0 1) GaAs surfaces by metalorganic molecular-beam epitaxy

Abstract

Atomically flat CdO thin layers were grown on GaAs(0 0 1) substrates with ZnS buffer layers. The grown layers were evaluated by reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM), X-ray rocking curve (XRC), and transmission electron diffraction (TED) measurements. The RHEED observations of CdO thin layers showed two-dimensional growth mode revealed by streaky patterns with excellent homogeneity through [1 1 0] and [ 1 ̄ 1 0] directions. This streaky pattern is the reflection of the flat surface morphology in atomic level assessed by AFM measurements with the surface root mean square roughness of ∼1 nm. The crystalline structure as well as quality of the thin CdO layers was investigated by X-ray diffraction and XRC measurements which indicated the single-crystalline rocksalt CdO thin layers with minimum full-width at half maximum under the optimal growth condition. The TED observation showed the epitaxial relationship between the rocksalt CdO and zincblende GaAs substrate as [1 1 0] CdO∥[1 1 0] GaAs, [1 1 ̄ 0] CdO∥ [1 1 ̄ 0] GaAs, and [0 0 1] CdO∥[0 0 1] GaAs.